1. Field Of The Invention
The present invention relates to novel plant growth enhancing compositions for stimulating various plant growth responses. More particularly, the invention relates to the use of plant growth enhancing compositions comprising a mixture of phytochemicals consisting of gibberellins, an auxin and a cytokinin for application to seed or foliage in order to stimulate seed germination or increase the overall development and yield of a variety of plant species.
2. Description Of The Prior Art
The growth and productivity of cultivated plants are known to be enhanced with the use of various growth stimulators. For example, there are known growth stimulators based on naturally occurring and synthetic auxins, such as indoleacetic acid and naphthaleneacetic acid, which induce stem elongation and promote root formation. Other synthetic auxins include 4-chloro-2-methylphenoxyacetic acid (MCPA); 2,4-chlorophenoxyacetic acid (2,4D); 2,4,5-trichlorophenoxyacetic acid (2,4,5-T); 2-(4-chloro-2-methyl-phenoxy) propionic acid (CMPP); 4-(2,4-dichlorophenoxy) butyric acid (2,4-DB); 2,4,5-trichlorobenzoic acid (TBA); and 3,5-dichloro-2-methoxybenzoic acid (dicamba), for example. All the above acids are active in the form of their salts and esters, such as their sodium, potassium, ammonium, dimethylamine and ethanolamine salts, and their lower alkyl esters. Many of these synthetic auxins are being used commercially as effective herbicides and some of them are known to adversely effect morphogenesis of treated plants.
Preparations based on cytokinins, such as 6-furfurylamino purine and 6-benzlyamino purine, are also known to be growth stimulators. However, cytokinins-based preparations which have a decisive influence in the stimulation of cell division seldom produce a desirable effect in the absence of auxins. While the mechanism by which cytokinins effect the growth cycle of plants is far from being understood, it is apparent that they affect leaf growth and prevent aging in certain plants. While the action of cytokinins on the growth of cultivated plants has been extensively studied, these plant hormones did not find wide application in plant raising since they must be applied at specific concentrations in parts per million. These critical rates of application render cytokinins-based preparations highly impractical in an agricultural environment.
Of all the known s mulators, the most widely used is a series of natural plant hormones generically named "gibberellins". The gibberellins are used for the acceleration or regulation of various stages of plant development, particularly growth, efflorescence, germination and parthenocarpy of higher plants. A series of related compounds identified as gibberellin A.sub.1 through A.sub.44 has been obtained by microbiological synthesis and the various compounds isolated from culture broth of Gibberella fujikuroi and from various plants including certain beans. The main component of the gibberellins used in practice is gibberellin A.sub.3, otherwise known as gibberellic acid.
While the gibberellins are highly effective as plant growth promoting or regulating substances, their use is greatly limited by their expense and insufficient effectiveness at low concentrations. As a result, considerable research has concentrated on efforts to find synergistic agents which can be used to enhance the activity of the gibberellins. One such synergistic agent for use with the gibberellins that have been discovered and put to practical use is described in U.S. Pat. No. 4,507,144 to Aloni. This patent discloses a composition consisting of the auxin naphthaleneacetic acid (NAA) and gibberellic acid (GA.sub.3) used for application to growing plants in order to increase the fiber content of the plants. However, the patented composition does not find wide application in plants other than those disclosed as being used as a source of commercial fibers and show little efficiency in stimulating growth, flowering and fructification of horticultural crops. Moreover, since the disclosed composition is applied to the plant as an aqueous spray, appreciably quantities of the composition flows down onto the soil and is not absorbed and assimilated in a systemic manner by the plant. Another disadvantage of the particular aqueous composition described by Aloni, which is especially specific when a spraying technique is employed, is the reduction of crop quality caused by the impossibility of attaining equally uniform application of the aqueous spray to various parts of the treated plant. A further disadvantage resides in the relatively high water requirements for the preparation of the reference compositions, the consumption of water being up to 800 liters per hectare.
The use of certain other gibberellin-based preparations in various forms for such specific applications as healing plant wounds, promoting flowering in apple trees and inducing plant growth in isolated sugar beet leaves is also known in the agricultural art. However, these known preparations do not find application over a wide range of crops and do not demonstrate a wide variety of plant growth enhancing properties.
There is, therefore, an urgent need for a growth enhancing composition consisting of synergistic agents for use with the gibberellins which enables a lower rate of application and displays a wide array of effects in the developmental processes of various agricultural and horticultural crops.